Upgrade to Pro — share decks privately, control downloads, hide ads and more …

How to create your own streaming torrent client with Python (for learning purposes)

How to create your own streaming torrent client with Python (for learning purposes)

A few years ago I created TouchAndGo [0] with Felipe Lerena and we learned a lot! I'll share some of that knowledge with you.
- What's BitTorrent? How does it work?
- Which libs you can use to find magnets links?
- How to handle magnet links;
- use libtorrent (API, tips, mis);
- download fast and be friendly with the torrent mesh.
- stream a video with Python;
- download subtitles;
- integrate all the parts together.

This talk is a rehash of one we did in 2014 with L1pe: https://www.youtube.com/watch?v=oMl1UiF_2Ss (The project is not maintained anymore).

[0] https://github.com/touchandgo-devs/touchandgo

Nicolás Demarchi

April 22, 2020

More Decks by Nicolás Demarchi

Other Decks in Technology


  1. How to create your own streaming torrent client with Python.

    (for learning purposes) Nicolás Demarchi - @gilgamezh 22/04/2020 - Python Ireland Meetup (online) https://www.meetup.com/pythonireland/events/270053115/
  2. Farewell Marcos Mundstock! Les Luthiers

  3. About me: Nicolás Demarchi https://py.amsterdam https://python.org.ar

  4. Disclaimer • This talk is a rehash of one we

    gave in 2014 with L1pe. I had to read all the code and translate it last weekend. • I’m not interested in having a philosophical discussion about torrent. This is a tech talk • I want to discuss how to build VOD using OSS
  5. What’s Bit Torrent? • It’s a decentralized protocol for file

    sharing (p2p) • Each client is a Peer that connects to a Tracker to find other Peers (in order) to download Pieces of a Torrent from them. More about it
  6. Torrent & Magnet • The first step to share a

    file using torrent is to generate a .torrent file. This file contains all the information for a Peer to find other Peers who are sharing the same file: hash value, size, filename(s), Tracker IP Address, size of the Pieces • A Magnet link contains the required information to ask and download the .torrent file from other clients.You don’t have to store/download the .torrent file • Each .torrent file has a unique 20-byte SHA-1 identifier.
  7. Peer • It’s an instance of a BitTorrent client that

    transfers data from and to other clients. • Seed: a Peer with 100% of the Pieces. • Leech: a Peer with < 100%.
  8. Tracker • It’s what the Peers use to get the

    initial list of other Peers sharing a file. • A Peer “announces” in a Tracker that it’s ready to interchange a torrent and the availability for it. • It’s the entry point to a Swarm • It’s possible to skip it using DHT
  9. Piece • A Piece is the exchange unit of a

    .torrent. • A .torrent has all the information about the size and amount of Pieces to download • Common size is between 64KB and 4MB • Each Piece has a SHA-1 unique identifier
  10. None
  11. How to get the magnet links https://github.com/harshanas/Py1337x

  12. How to download the torrent • tl;dr → libtorrent ◦

    BitTorrent C++ implementation ◦ Focus on performance and usability. ◦ Good docs.. ◦ PYTHON BINDING!! ◦ Easy to use. ◦ Available on any respectable OS (...and Windows).
  13. None
  14. • Session: libtorrent principal instance. It contains the main loop

    that controls all the torrents we are downloading. • Torrent Handle: It handles a particular .torrent. • Torrent Status: Contains all the information about the .torrent
  15. Some tips to understand how it works. • status.pieces() exposes

    a bitmask representing all the Pieces with a state (True if a piece was downloaded) • It’s possible to get/set the priority of a piece using handle.piece_priority() • The download queue is exposed at status.get_downlodad_queue(), status.download_rate() and status.upload_rate()
  16. None
  17. Strategy

  18. Piece picker • It’s who manages which Pieces are added

    to the download queue. • It has different strategies, rare first is the default. In this mode it always sets the highest priority to the pieces with less availability on the swarm. It’s the most solidary. • Each Piece has a priority from 1 to 7 (7 is highest) and a deadline (handle.set_piece_deadline() ). Both options affect the moment the Piece picker adds it to the download queue. • TIP: A Piece with a really low deadline will be downloaded ASAP.
  19. Video

  20. Torrent Streaming • VOD with BitTorrent. • How? : Downloading

    a video from the torrent network and serving it over HTTP to a local player. • How to server it over HTTP?: SimpleHTTPServer
  21. None
  22. Subtitles: subliminal and guessit https://pypi.python.org/pypi/subliminal/ Download subtitles in lots of

    languages using different providers https://pypi.python.org/pypi/guessit GuessIt is a python library that extracts as much information as possible from a video filename.
  23. None
  24. How to put all the parts together? pip install touchandgo

    https://github.com/touchandgo-devs/touchandgo We did it (in 2014): TouchAndGo.
  25. Last but not least This talk and TouchAndGo are really

    good example of the most important Python piece: The community. 60% of the work was already done ;-)
  26. Questions? mail@gilgamezh.me @gilgamezh